added cleaning_older_than descripton

README.md

@@ -109,20 +109,23 @@ Edit [configuration/dev_config.py](configuration/dev_config.py) rename it to you
 A personal collection contains a GEE collection `my_new_collection` which contains postprocessed sensor data. The postprocessing is done according to the ` <new_file>.<new_function_name>` . E.g. The product `ch.swisstopo-swisseo_vhi_v100` is based on the `COPERNICUS/S2_SR_HARMONIZED` collection which has been postprocessed with `step0_processor_s2_sr.generate_s2_sr_mosaic_for_single_date` and stored in the personal collection 'projects/username/assets/COL_S2_SR_HARMONIZED_SWISS'
 
 The personal collection needs to be created in advance in the GEE GUI via Assets -> new ->  Image collection
-**Note: if you wnat to ensure that other accounts can update/read the asset ( like satromo-int) you need to give them access via right click on asset which will then open https://console.cloud.google.com/iam-admin/iam?project=your-project and as well share "image collection" (like COL_S2_SR_HARMONIZED_SWISS)   **
+
+**Note:if you want to ensure that other accounts can update/read the asset ( like satromo-int) you need to give them access via right click on asset which will then open https://console.cloud.google.com/iam-admin/iam?project=your-project and as well share "image collection" (like COL_S2_SR_HARMONIZED_SWISS).**
 
 Adding a new collection in the tool require to adapt the configuration file. 
 
 A new function specifically designed for this new collections should also be added in the step0_processors folder.
 (If you don't need a new step0 processor function, you certainly don't need a new collection...)
 Create the new function in a new file located in step0_processors folder.
 In the configuration file, add the function to the configuration entry of your new collection:
+The `cleaning_older_than` removes asset older teh defiend days to save GEE storage. 
 
 ```
 step0: {
     ...
     my_new_collection: {
-        step0_function: <new_file>.<new_function_name>
+        step0_function: <new_file>.<new_function_name>,
+        cleaning_older_than: <days> 
     }
 }
 ```